Improved Oral Hygiene Reduces Hospital-Acquired Pneumonia Risk by 60% in Major Trial

The Hospital Acquired Pneumonia Prevention (HAPPEN) Study, a landmark multicenter trial involving 8,870 patients across nine wards in three Australian hospitals, demonstrates that improved oral hygiene reduces non-ventilator-associated hospital-acquired pneumonia risk by 60%. The 12-month stepped-wedge trial increased oral care delivery from 15.9% to 61.5% of patients by providing toothbrushes, educational materials, and staff training. Pneumonia incidence fell from 1.00 to 0.41 cases per 100 admission days-at-risk during the intervention period. Lead researcher Professor Brett Mitchell presented the results at ESCMID Global 2026, providing the first robust multicenter randomized controlled trial evidence supporting existing guidelines that recommend oral care for preventing this serious complication, which causes longer hospital stays, higher costs, and increased mortality.

HAPPEN Study Design and Scale

• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study was conducted over a 12-month period, concluding in August 2025.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study is the only multicenter randomized controlled trial in a hospital setting to evaluate oral hygiene for preventing non-ventilator-associated hospital-acquired pneumonia.
• ▪Each ward in the Hospital Acquired Pneumonia Prevention (HAPPEN) Study introduced the intervention every three months.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study was a multicenter, stepped-wedge cluster randomized controlled trial conducted across nine wards in three Australian hospitals.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study is the largest randomized controlled trial in a hospital setting to date for evaluating oral hygiene interventions.
• ▪4,347 patients in the Hospital Acquired Pneumonia Prevention (HAPPEN) Study were in wards during the intervention period.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study included 8,870 patients in total.

Intervention Methods and Oral Hygiene Improvements

• ▪Health care staff in the Hospital Acquired Pneumonia Prevention (HAPPEN) Study received onsite training, access to online resources and practical support to improve the delivery of oral care.
• ▪In the Hospital Acquired Pneumonia Prevention (HAPPEN) Study intervention phase, patients were provided on admission with a toothbrush, toothpaste, educational materials and access to additional online resources.
• ▪The proportion of patients receiving oral care in the Hospital Acquired Pneumonia Prevention (HAPPEN) Study increased from 15.9% in the control group to 61.5% in the intervention group.
• ▪Audits in the Hospital Acquired Pneumonia Prevention (HAPPEN) Study showed oral care was undertaken an average of 1.5 times per day during the intervention.

Pneumonia Risk Reduction and Clinical Mechanisms

• ▪Non-ventilator-associated hospital-acquired pneumonia is a form of pneumonia that develops at least 48 hours after hospital admission in patients who are not receiving mechanical ventilation.
• ▪Non-ventilator-associated hospital-acquired pneumonia incidence in the Hospital Acquired Pneumonia Prevention (HAPPEN) Study fell from 1.00 to 0.41 cases per 100 admission days-at-risk.
• ▪Non-ventilator-associated hospital-acquired pneumonia is linked to longer hospital stays, higher health care costs and increased mortality.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study showed that improving oral hygiene for hospital patients reduced the risk of non-ventilator-associated hospital-acquired pneumonia by 60%.

Implementation Challenges and Future Directions

• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study was presented at ESCMID Global 2026.
• ▪Professor Brett Mitchell is the lead study author of the Hospital Acquired Pneumonia Prevention (HAPPEN) Study and is affiliated with Avondale University, Australia.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study provides robust evidence from a hospital setting for oral care preventing non-ventilator-associated hospital-acquired pneumonia.

Perspective of Professor Brett Mitchell and HAPPEN Study researchers

• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study provides the robust evidence that has been missing to support existing guideline recommendations for oral care.
• ▪The Hospital Acquired Pneumonia Prevention (HAPPEN) Study demonstrates that a simple, low-cost intervention can prevent a serious hospital complication.

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